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To investigate the effect of manganese(Mn)on antioxidant status and expressions of heat shock proteins/factors in tissues of laying broiler breeders subjected to heat challenge,we used a completely randomized design(n=6)with a factorial arrangement of 2 environmental temperatures(normal,21 ± 1℃ and high,32 ± 1℃)× 3 dietary Mn treatments [a Mn-unsupplemented basal diet(CON),or a basal diet supplemented with 120 mg Mn/kg diet as inorganic Mn sulfate(iMn)or organic Mn proteinate(oMn)].There were no interactions(P>0.10)between environmental temperature and dietary Mn in all of the measured indices.High temperature decreased(P<0.003)Mn content,and also tended(P=0.07)to decrease copper zinc superoxide dismutase(CuZnSOD)activity in the liver and heart.However,an increased manganese superoxide dismutase(MnSOD)activity(P<0.05)and a slight increase of malondialdehyde level(P=0.06)were detected in breast muscle.Up-regulated(P<0.05)expressions of heat shock factor 1(HSF1)and HSF3 mRNA and heat shock protein 70(HSP70)mRNA and protein were found in all three tissues.Broiler breeders fed either iMn or oMn had higher tissue Mn content(P<0.0001),heart MnSOD and CuZnSOD activities(P<0.01)and breast muscle MnSOD protein levels(P<0.05),and lower(P<0.05)breast muscle HSP70 mRNA and protein levels than those fed CON.Broiler breeders fed oMn had higher(P<0.03)bone Mn content than those fed iMn.These results indicate that high temperature decreases Mn retention and increase HSP70 and HSFs 1,3 expressions in tissues of laying broiler breeders.Furthermore,dietary supplementation with Mn in either source may enhance heart antioxidant ability and inhibit the expression of HSP70 in breast muscle.Finally,the organic Mn appears to be more available than inorganic Mn for bone in laying broiler breeders regardless of environmental temperatures.